On Sun, 13 Oct 2013, Richard Knoppow wrote:


"gareth" wrote in message
...
Further information most welcome, thank-you

In the 1948 Radio handbook which I mentioned previously,
there are adverts
from a company by the name of Millen, and I assumed it was
the same guy
after he had left National.

Your comment about a phenolic intersperser is no doubt
some means of isolating an
earthy contact?

It would be interesting to know from the Lamb patent
whether he proposed therein the
technique of Single Signal Reception by the use of the
phasing control to null
out the audio image, or whether this was something that
came about through experience?


I think this was part of Lamb's original intention. The
articles originally describing the use of the filter were
aimed at "single signal" reception, meaning that the audio
image was suppressed. The Lamb filter required some juggling
between the bandwidth and phasing adjustments to get the
response to where the operator wanted it since they
interacted with each other and with the center frequency.
Nonetheless, the filter worked very well and provided an
order of magnitude better selectivity than was available
previously.
James Millen was one of the founders of National but
eventually was pushed out of the company. He started his own
company, also in Malden Mass, and probably made many parts
for National as well as his own stuff. Millen made very high
quality components. There is considerable history of both
National and Millen, including a Millen Society, on the web,
a Google search will find it.
The National HRO was a revolutionary receiver in its day
and stayed one of the favorites for both ham and commercial
use for some thirty years. The mechanical design is
attributed mostly to James Millen and the electronic design
mostly to Herbert Hoover Jr., son of the president of the
US.

And Hoover Jr. was president of the ARRL for a while.

Michael VE2BVW